1. Field of the Invention
The present invention relates to a motor-operated, direct-pressure type mold clamping mechanism of an injection-molding machine.
2. Description of the Related Art
An injection-molding machine is furnished with a toggle type mold clamping mechanism, in which a drive source and a moving platen are connected by means of a toggle link, or a direct-pressure type mold clamping mechanism, in which the drive source and the moving platen are connected directly. The clamping mechanism serves to open or close and clamp dies that are attached individually to the moving platen and a stationary platen.
In the mold clamping operation, the dies must be clamped with a strong force. Thus, a requisite for the drive source of a mold clamping mechanism is to be capable of producing a strong clamping force. In the process of injection molding, moreover, the time required for the manufacture of each molding, i.e, the cycle time, is relatively short. Another requisite for the drive source, therefore, is to be able to drive the dies at high speed while they are being opened or closed.
The toggle link acts to help the dies open or close at high speed, and to facilitate the production of a strong clamping force. Thus, the toggle type mold clamping mechanism fulfills both of the aforesaid requirements. The direct-pressure type mold clamping mechanism, on the other hand, has the advantage over the toggle type mold clamping mechanism in that the former does not require mold thickness adjustment for compensating the change of the die thickness. It is difficult for the direct-pressure type mold clamping mechanism, however, to satisfy both the aforementioned requirements. In the case of a direct-pressure type mold clamping mechanism using a motor as its drive source, for example, both of the aforementioned requirements can be fulfilled only if the motor used has a very large capacity, since large capacity motor are expensive, the manufacturing cost of the injection-molding machine increases.